LinkedIn is the premier social media site on the web for professionals. For those people who don't use Twitter, or find Facebook useless for business...LinkedIn can make them feel right at home.

It has a resume-like structure for its user profiles, the ability to share status updates, applications to share expertise, and groups that attract people from all sorts of professions, disciplines, alumni associations and interests. You can network from withing LinkedIn, connecting to colleagues, clients, friends, etc. Up to this point, however, LinkedIn's functions have all been internal to the service itself - including Groups.

"Groups" are great. They let you reach out and connect with others, ask and answer questions, share links, post photos and videos, etc. I moderate a couple and love the ability to connect with colleagues.

Earlier this month, LinkedIn took the intriguing step of giving groups the ability to become "open." Everything that's posted to an open group will now appear on the web, be found in search engines, and able to be shared via other social networking sites. You can post to an open Group, without being a member of that group.

This move has intriguing possibilities. It makes LinkedIn more of an "expertise portal." If people can see your insightful answers through a Google search, it can build your brand and credibility (and of course, the opposite is true as well!). On the other hand, it may act to inhibit the free exchange of ideas as well. I think since Facebook made all of your postings public on your friend's walls, that the quantity of interactions has greatly decreased. We'll see what happens with LinkedIn.